1. Field of the Invention
This invention relates to a thermoplastic resin for use in a coating resin to be coated on a base film to produce a magnetic recording tape, and more particularly to a thermoplastic resin which is a hydrolyzed product of vinyl chloride copolymer and a process for preparing such thermoplastic resin.
2. Prior Art
In the production of a magnetic recording tape, it is a known practice to mix a thermoplastic resin with a thermosetting resin to prepare a coating resin which is admixed with magnetic powders and then coated on a base film for the magnetic recording tape. As one example of the thermoplastic resin commonly used in such coating resin, there is known a hydrolyzed product of vinyl chloride copolymer having an average polymerization degree of from 400 to 500 said hydrolyzed product comprising 91% by weight of vinyl chloride, 3% by weight of vinyl acetate and 6% by weight of vinyl alcohol. Since the coating resin containing this known hydrolyzed product of vinyl chloride copolymer is inferior in elongation or covering power, it is unsatisfactory for use as the coating resin to be coated on a base film for producing a magnetic recording tape. Moreover, this prior art coating resin has a disadvantage in that magnetic powders can not be dispersed therein sufficiently uniformly to result in inferior reproducing power in high-frequency zone. Furthermore, it is poor in abrasion-proof property, adhesive power to the base film and durability such as physical strength, and thus fails to give a satisfactory magnetic recording tape.